The following are known examples of techniques for managing a plurality of power sources.
A power shut-off device for an analog circuit to which a plurality of power source voltages have to be supplied, for example, has been proposed. The power shut-off device includes current interruption units that are provided so as to correspond to power supply lines, respectively, and that each interrupt the flow of an overcurrent when the overcurrent flows through the line. The power shut-off device also includes current-interruption detection units that are provided so as to correspond to the current interruption units, respectively, and that each detect that a current flow has been interrupted by the current interruption unit. The power shut-off device also includes a logical unit that determines, based on an output signal from each current-interruption detection unit, whether or not to supply a power source voltage to the analog circuit. The power shut-off device also includes a switching unit that turns on or off output of a power source voltage to the analog circuit, based on a determination signal from the logical unit. When any one of the current-interruption detection units of power supply lines detects interruption of a current flow, the power shut-off device turns off output of a power source voltage of any line other than the line concerned.
An information processing device including a master electronic circuit, a slave electronic circuit coupled to the master electronic circuit, a second power source that supplies power to the slave electronic circuit through a system different from that of a first power source that supplies power to the master electronic circuit, and a power control circuit that controls power supply to the slave electronic circuit has also been proposed. In this information processing device, in a power saving mode, supply of power from the second power source to the servant electronic circuit is shut off and output of the second power source stops. In the power saving mode, in the case where an input signal is supplied to the master electronic circuit, a power control circuit supplies power from the second power source to the slave electronic circuit after a predetermined period has elapsed since resumption of output of the second power source.
A power supply management device including a control unit that controls a plurality of power sources has been proposed. The power supply management device includes power supply units that are provided for a plurality of power sources, respectively, and that each start supplying power based on a control signal output from the control unit, and output an OK signal to the control unit when supply of power has been normally started. The power supply management device also includes a shut-off unit that controls the power supply units to shut off all the power sources when a control signal from the control unit is not output in a predetermined period of time.
Examples of the related-art techniques are disclosed in Japanese Laid-open Patent Publication No. 5-207653, Japanese Laid-open Patent Publication No. 2008-117241, and Japanese Laid-open Patent Publication No. 2010-252444.
Recently, multiple-power-source devices, such as a field-programmable gate array (FPGA), to which a plurality of power source voltages are supplied have been used for many electronic apparatuses. An electronic apparatus including such a multiple-power-source device has a configuration in which a plurality of devices including a multiple-power-source device share power sources in order to realize size reduction and increased density. That is, regarding a power supply line for supplying a power source voltage, for example, of 1.5 V to a multiple-power-source device, another 1.5 V powered device may be connected to this line. Regarding another power supply line for supplying a power source voltage, for example, of 2.5 V to a multiple-power-source device, another 2.5 V powered device may be connected to this line.
For a plurality of power sources that supply power source voltages to a multiple-power-source devices, the order in which the plurality of power sources are turned on is determined in advance in some cases. Unintended operations (for example, the occurrences of a latch-up event and an excessive rush current) in a multiple-power-source device are prevented by appropriately setting the order in which the plurality of power sources are turned on.
In a multiple-power-source device, although power supply input terminals connected to power supply lines are isolated from one another, there may be a problem in that a voltage input to one power supply input terminal from a power source turned on first is input to another power supply input terminal. This may be due to, for example, formation of a parasitic element inside a semiconductor constituting a multiple-power-source device. Once such voltage re-direction occurs, a voltage appears in a power supply line connected to the other power supply input terminal at a timing earlier than a timing in accordance with the power supply sequence. Thus, there are some cases in which another device connected to the power supply line concerned is turned on at a timing earlier than the original timing and, as a result, a malfunction of the electronic apparatus occurs.
It is difficult to recognize, during the design phase, whether or not voltage re-direction has occurred in a multiple-power-source device. It is thus difficult to address this issue in advance. For this reason, in existing techniques, it is usual to check whether or not voltage re-direction is present and whether or not voltage re-direction affects another device, and the power supply sequence is then appropriately changed, if desired.
However, it is not easy to change a complex power supply sequence, and there are some cases where the issue is not solved merely by changing a power supply sequence.